Medical leads provide electrical stimulation from a medical device to a target site within a body of a patient. The medical device is typically implanted or otherwise installed on the body in an accessible area at some distance from the target site, and the medical lead is routed to the target site either through a percutaneous procedure or by surgical implantation depending upon the type and size of the medical lead being implanted.
Because the medical lead extends some distance between the medical device and the target site within the body, the medical lead is subject to forces imposed by movements of the patient. In particular, the medical lead may be subjected to strain. To address the strain, the medical lead may be routed by creating a loop that relieves the strain by the loop making available an additional length of the lead.
While this strain relief loop does relieve the strain, an issue occurs when the patient is subjected to radiofrequency (RF) electromagnetic energy in excess of the ambient, such as when having a magnetic resonance imaging (MRI) scan. The metal conductors within the lead, such as filars and/or a shield, have current induced by the RF energy. This induced current can produce heating within the medical lead but the heating is typically distributed over a length of an MRI conditionally safe lead and is not troublesome. However, with a strain relief loop, the heating tends to be more intense at the intersection point on the loop where the medical lead loops back onto itself. This more intense heating at the intersection point may produce discomfort or injury for the patient.